Will moving water freeze at the same temperature as still water ?
I believe that they should freeze at the same temperature. The difficulty will be one of measuring and controlling the temperature so that the moving body and the still body of water are similarly cooled. Given that the boundary layer between a fluid and any other material is stationary then the freezing process between say the air and the water will be the same whether the water is flowing or not. However the sheer stresses in the moving fluids will be a constant source of additional energy that will be reducing whatever cooling effort you provide. Experimentally it may be very difficult to compensate for this and result in still water freezing first. Unfortunately you can conclude nothing about the temperature at which the water freezes from this. If however you are only specifying the air temperature then I fully expect the flowing water to require a much lower air temperature before freezing occurs than the still water.
